In recent years, attention is being focused on the refractive index change phenomenon of a medium under irradiation with high-intensity laser light. This phenomenon causes a change in a spectrum of light when the laser light is injected into the medium. Knowing the position in the medium where such spectrum change occurs is useful for analysis of the phenomenon.
On the other hand, there is the known technology concerning scanning laser microscopes. The scanning laser microscopes are apparatus configured to focus laser light emerging from an optical fiber, on an object, receive fluorescence appearing from the object, by another optical fiber, and guide the fluorescence therethrough to a detector, and can obtain an image by moving the object or an imaging system to scan. The entire region of the object is scanned using a photodiode as the detector to obtain the image, and the fluorescence is again sampled at a point of interest on the image and guided to a spectroscope.
Such apparatus is described in “Tony Wilson & Colin Sheppard, THEORY AND PRACTICE OF SCANNING OPTICAL MICROSCOPY (Academic press, England, 1984, pp. 173-175)” and “New Optical Microscopes, p. 31, supervised by Tetsuya Fujita and edited by Satoru Kawada, Gakusai Kikaku K.K.”
There are also some known techniques of extracting light corresponding to a specific point in the microscopic field and measuring a spectrum thereof. In the ordinary microscope system, light collimated by an objective optical system is split into two beams by a light splitting optical system, one beam is guided through an imaging optical system to a camera, and the other beam is guided similarly through an imaging optical system to an optical fiber. It is preliminarily determined which point on pixels of the camera corresponds to the position of the end face of the optical fiber (an aperture), and this point is marked on an image obtained from the camera, whereby correspondence can be made between the position and the light sampled by the optical fiber.
For example, an XY stage is moved to bring a point of interest to the position marked on the image, and the point of interest is exposed to the light. Such apparatus is described in the foregoing document [Tony Wilson & Colin Sheppard, THEORY AND PRACTICE OF SCANNING OPTICAL MICROSCOPY (Academic press, England, 1984, pp. 176-177)].